The invention relates to devices and methods for delivering, administering or dispensing substances, including such devices and methods involving osmotic drive. More particularly, it relates to an automatic hydrogel-based extracorporeal fluid conveyor, in particular example for the delivery or output of insulin, which has a simple structure and small dimensions and time and conveying characteristics which can be adjusted by the user. In some embodiments the device or conveyor is intended for a single use and, in other embodiments, it is capable of use more than once.
It is estimated that there are several million people with chronic diseases living today in Germany alone. Of these, several hundred thousand belong to the type of patient who requires constant medication. Such a patient has a continuous basic requirement for one or more active substances. The individually determined basic requirement, which typically may be or is injected subcutaneously with a syringe, is necessary to ensure that the person affected is able to maintain a normal situation. In addition to this basic requirement, a further requirement for administration of active substances exists in some cases.
Using electromechanically, pneumatically or osmotically driven dosing systems or devices for administrating, delivering, conveying or injecting medication on a permanent and continuous basis is known.
WO 93/16740 discloses an electromechanically operated injection pen. It was developed for self-medication with liquid injectable medicaments or auxiliaries. The liquid is expelled by a piston which is coupled to a spindle and which is driven forward by motor force. The disadvantage of these previously known devices lies in their complex structure and the fact that they are dependent on an energy supply by means of a battery.
DE 41 06 624 discloses an osmotically operated injection system for slow and steady injection of medication. The syringe piston is in this case driven forward via salination or osmotic forces. A fluid of higher concentration is diluted, with increase in volume, as a result of osmotic uptake of a fluid of lower concentration. The working pressure thereby generated is used for driving the piston forward. The functionality is impaired by movable protruding parts and by the absence of a mechanism for delaying activation and triggering. No pulsatile operation is possible with this pump.
An osmotically driven, portable extracorporeal infusion pump is likewise disclosed in U.S. Pat. No. 5,672,167. It comprises two storage pouches: the fluid to be conveyed is accommodated in one of them, and the second pouch contains the driving liquid. Salination or osmotic forces from the concentration equilibrium of two liquids are again used for conveying the fluid. The infusion rate is dependent on the properties of the semipermeable membrane lying in between and must therefore be pre-set at the time of production. The pump is activated by a valve or by the destruction of a seal. Pulsatile operation is possible only by using conventional powered and timed pumps.
U.S. Patent application 2001047161 describes an implantable and osmotically operated system for the administration of medicaments. It is used for long-term administration of liquid or soluble medication. The output characteristic is set, at the time of production, by the choice of membrane and by the material properties of the swelling substance. It is not possible for the physician to subsequently adjust the release time and subsequently adapt the conveying characteristics to the demands of the patient.
U.S. Pat. No. 5,340,590 has already disclosed pump systems which, through a combination of several layers of different osmotic and swelling substances, permit pulsatile operation of the pump. The characteristic curve can be adapted to the patient requirements only during production. The pump system does not have its own swelling agent reservoir and is therefore based on moisture being taken up from the surrounding medium. It is therefore designed only as an implant or as a capsule to be ingested. No delayed release or switch-on mechanism is indicated.
In U.S. Pat. No. 5,209,746, the pulsatile operation of an osmotic pump is achieved by structural means such as constrictions or mechanical barriers. The disadvantages of these systems are that the characteristic curve of the pump can be adapted to the patient requirements only at the time of production and the fact that they are limited to intracorporeal use because of the absence of a swelling agent reservoir. No delayed release or switch-on mechanism is indicated.
A delayed release for osmotically operated pumps is disclosed in U.S. Pat. No. 4,976,966. This is achieved by a pump core with a semipermeable membrane and an osmotic drive being pressed out of an impermeable sleeve.
The pressing out is likewise effected by an osmotic drive situated at the bottom of the outer sleeve. The outer sleeve is perforated or of semipermeable design at its base. This delayed release cannot be adjusted by the user and the pump functions only within a moist environment, i.e. when implanted or in the digestive tract.
While they may be well-suited for their intended purpose, the above-mentioned devices have a number of drawbacks. It is true that extracorporeal insulin pumps have very many adjustment functions and individually adaptable program sequences, but they are of very complicated design and are therefore expensive and generally require external power. The described implantable drug delivery systems operating according to the principle of osmotic pumps are of very simple construction. However, a disadvantage of these is the implantation, which is always associated with high costs and risks, and the impossibility of the patient being able to adjust the pump output characteristic. These devices can also only cover the basic requirement of the patient.